A plasma processing technology has been widely used for many semiconductor devices such as an integrated circuit, a liquid crystal display and a solar cell. Although the plasma processing technology has been used for thin film deposition process or an etching process in a semiconductor manufacturing process, a highly advanced plasma process is required for a product having a higher performance and multi function (for example, an ultra fine process technology). In particular, a microwave plasma processing apparatus capable of generating plasma of low pressure and high density has drawn attention.
A plasma processing apparatus using a RLSA (Radial Line Slot Antenna) plasma microwave source ionizes a gas by microwave discharge and generates plasma. A microwave is supplied through slots of the antenna via a waveguide, propagated through a top plate, and radiated into a plasma generation chamber.
If the top plate is simple and flat, the microwave is not uniformly propagated in a central portion and a peripheral portion of the top plate, and, thus, plasma cannot be uniformly generated. On the other hand, if the top plate has different thicknesses in different portions or has a protruded portion therein, a resonance area of the microwave is formed depending on a plasma condition, and, thus, propagation in a diametric direction can be controlled.
The microwave within the top plate is propagated simultaneously in a diametric direction and in a circumferential direction (a rotation direction). So far, a subject of microwave propagation control has been mainly focused on propagation in a diametric direction as disclosed in Patent Document 1. As a result, there has been a problem in that plasma is non-uniformly distributed due to non-uniformity of propagation in a circumferential direction. In particular, such a phenomenon becomes serious at a low microwave power. Further, in order to control propagation in a diametric direction and propagation in a circumferential direction at the same time, a shape of the top plate becomes complicated, which causes an increase in manufacturing costs.
Patent Document 1: Japanese Patent Laid-open Publication No. 2005-100931